Believing in creationism is a sin

[Esquilax]

Even if Adam and Eve had thousands of sons and daughters, the earth would only become populated beyond the first family by way of incest. After all, there is no mention of God having created any other humans besides Adam and Eve.

You are correct to the point of bothers and sisters marrying and having children, at the time it was not considered incest, the gene pool was nearly perfect and began to be degraded with time. This was due to sin and it's continued effect on mankind.

What is it that you think incest means? It has nothing to do with the purity of the gene pool; definitionally, if a brother marries his sister, that's incestuous. I understand your need to retreat from that word in relation to your creation story, but perfect genes or not (incidentally there's no mention of genes in the bible, and hence you're not really pulling that idea from the official source, there. You're just making up an excuse that feels better.) it's still an incestuous story.

Or are you saying that if a brother and sister wanted to get married today you wouldn't consider it incest so long as their genes were perfect?